1. Field of the Invention
The present invention relates to hydraulic equipment or a power transmission device widely available in each of industrial fields, such as industrial equipment or a vehicle.
2. Background Art
Conventionally, there is well known an art of hydraulic equipment comprising a first rotary shaft and a second rotary shaft; first and second plungers which are moved reciprocally axially; first and second spool valves which are also moved reciprocally axially; a cylinder block which houses the first and second plungers and the first and second spool valves and is rotated integrally with the first rotary shaft; a first swash plate which touches the first plungers at a swash plate surface changeable its slant angle against the axis of the rotary shaft; and a second swash plate which touches the second plungers at a swash plate surface having the fixed slant angle against the axis of the rotary shaft and is rotated integrally with the second rotary shaft, wherein a hydraulic circuit is formed in the cylinder block so as to communicate holes in which the first plungers are housed with holes in which the second plungers are housed, and a passage of pressure oil flowing into or out from the plunger holes in which the input side plungers are housed is switched by the first spool valves, and a passage of pressure oil flowing into or out from the plunger holes in which the second plungers are housed is switched by the second spool valves. For example, such an art is disclosed in the Japanese Patent Laid Open Gazette 2003-14079.
With regard to the above-mentioned hydraulic equipment, one of important factors determining the driving characteristics (energy efficiency, noise, friction and the like) is the timing of switching an oil passage of hydraulic circuit in the cylinder block by the first spool valve (input side spool valve) and the second spool valve (output side spool valve). Accordingly, high accuracy is required of the control of reciprocal movement of the first and second spool valves, whereby high dimensional accuracy is required of the parts concerning to the reciprocal movement along the axial direction of the input shaft.
With regard to the hydraulic equipment disclosed in the Japanese Patent Laid Open Gazette 2003-14079, the spool valve is moved reciprocally along the axial direction of the input shaft by an engaging member (retainer) engaged with the spool valve provided in the cylinder block so as to switch passages of the hydraulic circuit. The engaging member is rotatably attached to a holder through a ball bearing, and the holder is supported by a side wall member (a member for pivotally supporting the input shaft and attaching the hydraulic equipment to a transmission casing or the like). Furthermore, a member for keeping distance between the side wall member and the cylinder block (sleeve) is provided. Accordingly, the number of parts concerning to the accuracy of the reciprocal movement of the spool valve is many, whereby it is difficult to keep the accuracy and the manufacturing cost is increased.